ChainingClassExternalizerFactory.java

/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jboss.marshalling;

import java.util.Collection;
import java.util.Iterator;

/**
 * A class externalizer factory that tries each delegate externalizer factory in sequence, returning the first match.
 */
public class ChainingClassExternalizerFactory implements ClassExternalizerFactory {
    private final ClassExternalizerFactory[] externalizerFactories;

    /**
     * Construct a new instance.
     *
     * @param factories a collection of factories to use
     */
    public ChainingClassExternalizerFactory(final Collection<ClassExternalizerFactory> factories) {
        externalizerFactories = factories.toArray(new ClassExternalizerFactory[factories.size()]);
    }

    /**
     * Construct a new instance.
     *
     * @param factories a collection of factories to use
     */
    public ChainingClassExternalizerFactory(final Iterable<ClassExternalizerFactory> factories) {
        this(factories.iterator());
    }

    /**
     * Construct a new instance.
     *
     * @param factories a sequence of factories to use
     */
    public ChainingClassExternalizerFactory(final Iterator<ClassExternalizerFactory> factories) {
        externalizerFactories = unroll(factories, 0);
    }

    /**
     * Construct a new instance.
     *
     * @param factories an array of factories to use
     */
    public ChainingClassExternalizerFactory(final ClassExternalizerFactory[] factories) {
        externalizerFactories = factories.clone();
    }

    private static ClassExternalizerFactory[] unroll(final Iterator<ClassExternalizerFactory> iterator, final int i) {
        if (iterator.hasNext()) {
            final ClassExternalizerFactory factory = iterator.next();
            final ClassExternalizerFactory[] array = unroll(iterator, i + 1);
            array[i] = factory;
            return array;
        } else {
            return new ClassExternalizerFactory[i];
        }
    }

    /** {@inheritDoc}  This implementation tries each nested externalizer factory in order until a match is found. */
    public Externalizer getExternalizer(final Class<?> type) {
        for (ClassExternalizerFactory externalizerFactory : externalizerFactories) {
            final Externalizer externalizer = externalizerFactory.getExternalizer(type);
            if (externalizer != null) {
                return externalizer;
            }
        }
        return null;
    }
}